Generally, in the technology regarding oxide semiconductor thin film transistor (TFT), a back channel etch (BCE) structure or an etch stop layer (ESL) structure is employed for forming a metal oxide semiconductor TFT, and a mask process and an etching treatment process need to be conducted separately for both an active layer and source and drain electrodes. Consequently, this requires a relatively long process time for manufacturing a TFT, a relatively large step, and a relatively high cost.